I propose to study meiosis and genetic recombination in the mushroom, Coprinus cinereus. The goals of my research program are to demonstrate the precise time of crossing over using the tools of molecular biology, to determine if the meiotic chromosomes are transcriptionally active and study the control of such transcription, to isolate the synaptonemal complex for studies of its function, and to characterize mutations in Coprinus which are defective in the meiotic processs. Coprinus is ideally suited for these studies since meiosis occurs synchronously in external basidial cells, the cytological features of the relatively long meiotic prophase are easily visible in the light microscope, the DNA content is relatively low, and the genetic characterization of this organism is reasonably advanced.